Application of an in-hospital, surgeon-led anti-osteoporotic medication algorithm in patients with hip fractures improves persistence to medication and can prevent the second fragility fracture.

INTRODUCTION: Secondary fracture prevention is an essential part of hip fracture treatment. Despite this, many patients are discharged without the appropriate anti-osteoporotic medication. The aim of this study is to report the outcomes of the application of an in-hospital, surgeon-led anti-osteoporotic medication algorithm to patients with hip fractures. MATERIALS AND METHODS: This prospective cohort study followed patients with hip fractures who were treated at a tertiary referral hospital between 2020 and 2022. At discharge, anti-osteoporotic medication according to the Arbeitsgemeinschaft für Osteosynthesefragen (AO) Foundation algorithm was prescribed to all patients. Multivariate Cox regression analysis was used to investigate the risks of non-persistence to medication and of secondary fracture. RESULTS: Two hundred thirteen consecutive patients were prospectively followed. Mean follow-up was 17.2 ± 7.1 months. Persistence to medication at 2 years was 58% (95%CI 51-65%). A secondary osteoporotic fracture occurred in 1/126 (0.8%) persistent patients and 9/87 (11.4%) non-persistent patients. Multivariable Cox regression analysis confirmed that persistence to medication was significantly associated with a lower risk of secondary fracture (cause-specific hazard ratio [csHR] 0.05; 95%CI 0.01-0.45; p = 0.007). CONCLUSION: The application of the surgeon-led AO Foundation algorithm enables the in-hospital initiation of anti-osteoporotic treatment, leading to better persistence to medication and decreased incidence of secondary osteoporotic fractures.

Revision of a Failed Primary Total Hip Arthroplasty following Excessive Reaming with a Medial Cup Protrusion.

Background and Objectives: Atraumatic intrapelvic protrusion of the acetabular component following excessive reaming of the acetabulum with a far medial positioning of the cup is a rare, but serious complication of a total hip arthroplasty (THA). This study analyzes the factors contributing to this uncommon complication and presents the outcome after the revision surgery using the Ganz reinforcement ring combined with a bone graft and plating of the posterior column and/or screws for the anterior column. Materials and Methods: A retrospective case series study with seven patients (four males, mean age 76 ± 10 years (60−86)) that underwent a revision THA within 24 ± 17 days (5−60) after an atraumatic periprosthetic acetabular fracture with a medial cup protrusion was performed. All fractures were reconstructed with a Ganz reinforcement ring and bone graft with a mean follow-up of 1.7 ± 1.7 years (0.5−5). Radiographs were evaluated for the following: (i) cup positioning immediately after the primary THA and the revision surgery, (ii) cup migration in the follow-up, and (iii) fracture healing. Results: The position of the acetabular component as assessed on the postoperative radiographs after the index surgery and before the complete medial cup protrusion showed a cup placement beyond the ilioischial line indicative of a fracture of the medial wall. The revision surgery with the reconstruction of the medial wall with a Ganz reinforcement ring combined with a bone graft restored in the presented cases the center of rotation in the horizontal direction with a statistical significance (p < 0.05). During the follow-up, there was no aseptic loosening with the relevant cup migration or significant change in the position of the acetabular cup at the final follow-up (p > 0.05) after the revision. All seven fractures and bone grafts realized a bone union until the latest follow-up. Conclusions: Following excessive reaming, the acetabular component was placed too far medially and resulted in an intrapelvic cup protrusion. An unstable cup following a fracture of the medial wall was evident on the immediate postoperative radiographs. In the case of the medial wall perforation with an intrapelvic cup protrusion after the primary THA, the reconstruction with a Ganz reinforcement ring was a successful treatment option resulting in the fracture healing and a stable cup positioning. Surgeons should be aware of that rare and probably underreported complication and restore the anatomic center of rotation by treating the defect intraoperatively.

Direct anterior decompression of L4 and L5 nerve root in sacral fractures using the pararectus approach: a technical note.

PURPOSE: To describe a new surgical technique for neurolysis and decompression of L4 and L5 nerve root entrapment after vertical sacral fractures via the pararectus approach for acetabular fractures, and to present four case examples. PATIENTS AND METHODS: We retrospectively evaluated four patients suffering radiculopathy from entrapment of the L4 or L5 nerve root in vertical sacral fractures between January and December 2016. The mean follow-up period after surgery was 18 (range 7-27) months. All patients underwent direct decompression and neurolysis of the L4 and L5 nerve roots via the single-incision, intrapelvic, extraperitoneal pararectus approach. RESULTS: In all patients, the L4 and L5 nerve root was successfully visualized and decompressed, proving feasibility of the pararectus approach for this indication. No patient presented with a neural tear. Complete neurologic recovery was present in one patient at last follow-up; two patients had incomplete recovery of their radiculopathy; and one patient had no improvement after nerve root decompression. CONCLUSIONS: The pararectus approach allows for sufficient visualisation and direct decompression and neurolysis of the L4 and L5 nerve root entrapped in vertical sacral fractures. Although neurologic recovery was not achieved in all patients in this small case series, the approach may be a suitable alternative to posterior approaches and other anterior approaches such as the lateral window of the ilioinguinal approach.

Extracortical plate fixation with new plate inserts and cerclage wires for the treatment of periprosthetic hip fractures.

PURPOSE: Fixation of periprosthetic hip fractures with intracortical anchorage might not be feasible in cases with bulky implants and/or poor bone stock. METHODS: Rotational stability of new plate inserts with extracortical anchorage for cerclage fixation was measured and compared to the stability found using a standard technique in a biomechanical setup using a torsion testing machine. In a synthetic PUR bone model, transverse fractures were fixed distally using screws and proximally by wire cerclages attached to the plates using "new" (extracortical anchorage) or "standard" (intracortical anchorage) plate inserts. Time to fracture consolidation and complications were assessed in a consecutive series of 18 patients (18 female; mean age 81 years, range 55-92) with periprosthetic hip fractures (ten type B1, eight type C-Vancouver) treated with the new device between July 2003 and July 2010. RESULTS: The "new" device showed a higher rotational stability than the "standard" technique (p < 0.001). Fractures showed radiographic consolidation after 14 ± 5 weeks (mean ± SD) postoperatively in patients. Revision surgery was necessary in four patients, unrelated to the new technique. CONCLUSION: In periprosthetic hip fractures in which fixation with intracortical anchorage using conventional means might be difficult due to bulky revision stems and/or poor bone stock, the new device may be an addition to the range of existing implants.

Surgical fixation of ipsilateral femoral neck and shaft fractures: a matter of debate?

Segmental femoral fractures represent a rare but complex clinical challenge. They mostly result from high-energy mechanisms, dictate a careful initial assessment and are managed with various techniques. These often include an initial phase of damage control orthopaedics while the initial manoeuvres of patient and soft tissue resuscitation are employed. Definitive fixation consists of either single-implant (reconstruction femoral nails) or dual-implant constructs. There is no consensus in favour of one of these two strategies. At present, there is no high-quality comparative evidence between the various methods of treatment. The development of advanced design nailing and plating systems has offered fixation constructs with improved characteristics. A comprehensive review of the existing evidence with a step-by-step description of these different definitive fixation strategies based on three case examples was conducted. Furthermore, the rationale for using single vs dual-implant strategy in its case is presented with supportive references. The prevention of complications relies mainly on the strict adherence to basic principles of fracture fixation with an emphasis on careful preoperative planning, the quality of the reduction, and the application of soft tissue-friendly surgical methods.

Computer-assisted femoral head-neck osteochondroplasty using a surgical milling device an in vitro accuracy study.

Surgical navigation might increase the safety of osteochondroplasty procedures in patients with femoroacetabular impingement. Feasibility and accuracy of navigation of a surgical reaming device were assessed. Three-dimensional models of 18 identical sawbone femora and 5 cadaver hips were created. Custom software was used to plan and perform repeated computer-assisted osteochondroplasty procedures using a navigated burr. Postoperative 3-dimensional models were created and compared with the preoperative models. A Bland-Altmann analysis assessing α angle and offset ratio accuracy showed even distribution along the zero line with narrow confidence intervals. No differences in α angle and offset ratio accuracy (P = 0.486 and P = 0.2) were detected between both observers. Planning and conduction of navigated osteochondroplasty using a surgical reaming device is feasible and accurate.

Staged treatment of a comminuted femoral fracture with Masquelet technique and 3D printed reposition guides.

Background: Comminuted femoral fractures pose a challenge to the trauma surgeon due to the absence of bony references during surgery. Therefore, malalignment of length and axis can occur and necessitate revision surgery. During the last decade, 3D-planning has evolved as a surgical aid in difficult cases. Case report: An 18-year-old male patient suffered a polytrauma following a motorcycle accident. This report is about the treatment of a 3rd degree open and comminuted fracture of the left distal femur. The fracture was treated with Masquelet's two-staged technique. With the intent of avoiding malalignment, the second stage surgery was performed with the aid of 3D-planned reduction guides. Despite complex fracture pattern, complete fracture union was achieved with acceptable final alignment (side-to-side comparison of length, axis and femoral torsion). Conclusion: In this case, performing Masquelet's two-staged surgery with the aid of 3D-printed reposition guides yielded favorable results in regards to rotational malalignment. The malrotation of the femur was reduced after the second operation to a clinically acceptable side-to-side difference (10°). This technique remains technically challenging due to soft tissue tension and limited possibility of soft tissue release.

Sciatic nerve injury after acetabular fractures: a meta-analysis of incidence and outcomes.

PURPOSE: To investigate the incidence and the outcome of post-traumatic and iatrogenic sciatic nerve palsy (SNP) associated with fractures of the acetabulum. The results of sciatic nerve grafting for treatment were also investigated. METHODS: PUBMED, SCOPUS and COCHRANE databases were searched for longitudinal observational studies reporting sciatic nerve palsy related to acetabular fractures in adult patients over the last 20 years. Data regarding patients demographics, type of acetabular fracture, rate of post traumatic and iatrogenic sciatic nerve palsies as well as recovery rate are reported. Studies were assessed for their quality. Random effects meta-analyses were carried out to pool overall proportions of SNP incidence and complete recovery. Variations in SNP incidence by main study characteristics were assessed by subgroup analysis and meta-regression. A narrative review of sciatic nerve grafting was also conducted. RESULTS: Twenty studies reporting 44 post-operative and 18 iatrogenic SNPs in 651 patients were reviewed. The pooled incidence of posttraumatic SNP was 5.1% (95% CI 2.7-8.2%). The pooled incidence of iatrogenic SNP was 1.4% (95% CI 0.3-2.9%). Complete recovery of post-traumatic and iatrogenic SNP occurred in 64.7% (95% CI 41.7-85.4%) and 74.1% (95% CI 31.5-100%), respectively. CONCLUSION: A favorable outcome of both post-traumatic and iatrogenic SNP related to acetabular fractures has been found. Due to the poor results of sciatic nerve grafting, a "wait and see" approach may be the best option, in cases of a contused but anatomically intact sciatic nerve.

Lower 1-Year Postoperative Mortality After Acetabular Versus Proximal Femoral Fractures in Elderly Patients.

BACKGROUND: Geriatric acetabular fractures are becoming more common due to demographic changes. Compared with proximal femoral fractures, surgical treatment is more complex and often does not allow full-weight-bearing. The aims of this study were to compare operatively treated acetabular and proximal femoral fractures with regard to (1) cumulative 1-year mortality, (2) perioperative complications, and (3) predictive factors associated with a higher 1-year mortality. METHODS: This institutional review board-approved comparative study included 486 consecutive surgically treated elderly patients (136 acetabular and 350 proximal femoral fractures). After matching, 2 comparable groups of 129 acetabular and 129 proximal femoral fractures were analyzed. Cumulative 1-year mortality was evaluated through Kaplan-Meier survivorship analysis, and perioperative complications were documented and graded. After confirming that the proportionality assumption was met, Cox proportional hazard modeling was conducted to identify factors associated with increased 1-year mortality. RESULTS: The acetabular fracture group had a significantly lower cumulative 1-year mortality before matching (18% compared with 33% for proximal femoral fractures, log-rank p = 0.001) and after matching (18% compared with 36%, log-rank p = 0.005). Nevertheless, it had a significantly higher overall perioperative complication rate (68% compared with 48%, p < 0.001). In our multivariable Cox regression analysis, older age, perioperative blood loss of >1 L, and wheelchair mobilization were associated with lower survival rates after acetabular fracture surgery. Older age and a higher 5-item modified frailty index were associated with a higher 1-year mortality rate after proximal femoral fractures, whereas postoperative full weight-bearing was protective. CONCLUSIONS: Despite the complexity of operative treatment and a higher complication rate after acetabular fractures in the elderly, the 1-year mortality rate is lower than that after operative treatment of proximal femoral fractures, even after adjustment for comorbidities. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Transfer of osteochondral shell autografts to salvage femoral head impaction injuries in hip trauma patients.

INTRODUCTION: Femoral head impaction defects are observed with variable severity, as a result of traumatic hip dislocations which can be caused by traffic accidents or seen in professional athletes amongst other mechanisms. Compression of the articular cartilage and the subchondral bone into the femoral head results in irregular articular surfaces influencing the outcome with predisposition to osteoarthritis, and being predictive for the need for delayed total hip replacement. This study reports the outcome after a minimum follow-up (FU) of five years in a consecutive series treated with transfer of osteochondral shell autografts in hips (TOSAH) from the head-neck junction into the defect using surgical hip dislocation. PATIENTS AND METHODS: Between 06/2007 and 03/2014 a series of twelve consecutive patients (mean age: 35yrs, range 18-53; median Injury Severity Score: 12, range 9-27) sustained a traumatic posterior hip dislocation in combination with acetabular and/or Pipkin fractures and were inter alia treated using TOSAH using surgical hip dislocation. Conversion to total hip replacement (THR) during FU was noted as failure. Patients were clinically (Merle d'Aubigné score) and radiographically assessed for occurrence of osteoarthritis (OA), avascular necrosis (AVN) and/or heterotopic ossification (HO) at a minimal follow-up of five years. RESULTS: Mean follow-up was 6.9 years (5.0-11.6). At five-year follow-up, we found a survivorship of 57.1% (95% Confidence interval {CI}, 46.7-100%). Four patients required conversion to a total hip replacement at 11, 16, 28 and 44 months respectively after the TOSAH procedure due to osteoarthritis progression. One patient required conversion to a total hip replacement 12 months after TOSAH procedure due to AVN. One patient was lost to follow-up after 2.7 years. The remaining six patients with preserved hips presented with a median Merle-d'Aubigné score of 16 points (range: 14-18) and no AVN. Two patients showed asymptomatic grade I osteoarthritis according to Tönnis at latest follow-up and three patients showed mild asymptomatic HO according to Brooker (Grade I-II). CONCLUSION: The presented technique can be used as a salvage procedure for severely injured hip joints and to preserve the hip joint at midterm with satisfying clinical and radiological outcomes.

Stepped osteotomy of the trochanter for stable, anatomic refixation.

Refixation of a trochanteric osteotomy carries a high complication rate. To enhance stability and facilitate anatomic reduction of the trochanteric fragment, we have introduced a stepped osteotomy. Between April 2006 and June 2007, we performed surgical hip dislocations using the modified trochanteric osteotomy combined with a relatively aggressive rehabilitation program. Full weightbearing was allowed at a mean of 42 days (range, 33-54 days). The minimum followup was 8 months (median, 13 months; range, 8-24 months). Postoperative radiographs were assessed prospectively for consolidation or the appearance of malreduction/nonunion/malunion of the osteotomy and heterotopic ossification. In 110 of 113 hips, the trochanteric osteotomy healed in the anatomic position. Two patients had a trochanteric delayed union with loss of anatomic position, and one additional patient underwent revision surgery for a pseudarthrosis and cranial migration of the trochanteric fragment. All three complications related to healing occurred in the first 60 patients when the step height was 3 to 4 mm. After increasing the step heights to 6 mm, we observed no healing complications. Despite more aggressive postoperative mobilization, the incidence of malunion or nonunion related to the new stepped osteotomy is low and approaches zero for steps of 6 mm. It is now our technique of choice.

Osteosynthesis and hemiarthroplasty of fractures of the proximal humerus: outcomes in a consecutive case series.

HYPOTHESIS: This study addresses the outcome after osteosynthesis or hemiarthroplasty, using a cohort of patients that was enrolled in a previous prospective study on humeral head perfusion and was consequently treated using a common conceptual approach. MATERIALS AND METHODS: Between 1998 and 2001, 98 patients with 100 fractures of the proximal humerus were treated surgically by a single surgeon with open reduction and internal fixation (ORIF) (51/100, group A, median age 54 years; range, 21-88) or with hemiarthroplasty (49/100, group B, median age 66 years; range, 38-87). Seventy-six of 98 patients were available for re-evaluation at a mean follow-up of five years (3.3-7.3) using the Constant-Murley score (CMS), the Subjective Shoulder Value (SSV), and conventional radiographs. RESULTS: The median total CMS was 77 (range, 37-98) for group A and 70 (range, 39-84) for group B. The median SSV was 92 (range, 40-100) for group A and 90 (range, 40-100) for group B. Avascular necrosis occured in 6/40 fractures treated with ORIF. CONCLUSION: Osteosynthesis and hemiarthroplasty yield similar functional results and comparable patient satisfaction following the applied decision making process in this selected patient cohort. Osteosynthesis with preservation of the humeral head is worth considering when adequate reduction and stable conditions for revascularization can be obtained. In patients with osteopenic bone and/or comminuted fractures, hemiarthroplasty is a viable alternative. LEVEL OF EVIDENCE: Level 2; Prospective non-randomized comparison study.

Surgical Hip Dislocation for Exposure of the Posterior Column.

BACKGROUND: Surgical hip dislocation is performed for safe and efficient management of acetabular fractures predominantly involving the posterior column. The dislocation of the femoral head allows for direct visualization of the hip joint during fracture treatment. DESCRIPTION: The patient is placed in the lateral decubitus position with sterile preparation and draping of the ipsilateral leg to allow for dislocation. The skin incision is straight and centered over the greater trochanter. After the skin incision, the interval between the gluteus maximus and medius muscles is developed. The sciatic nerve is identified, and special attention to the course of the medial circumflex femoral artery is given during dissection of the piriformis and triceps coxae muscles (obturator internus and superior and inferior gemelli muscles). The latter are incised 2 cm posterior to their insertion on the posterior aspect of the greater trochanter. The vastus lateralis muscle belly is elevated from the lateral femoral shaft, and a trochanteric osteotomy is performed. The trochanteric medallion is rotated 90°, and the gluteus minimus muscle is released from the capsule. After complete exposure of the hip capsule, a z-shaped capsulotomy is performed whereby any injury to the posterior capsular attachments of a posterior wall fragment is avoided. The posterior column and the greater and lesser sciatic notches are exposed, with the sciatic nerve under protection. The femoral head is dislocated either anteriorly or posteriorly to obtain direct visualization of the hip. Reduction begins at the articular surface, in cases of marginal impaction, and proceeds to the posterior wall and/or posterior column and the anterior column, when involved. For fixation, 3.5-mm cortical screws acting as positioning or lag screws and reconstruction plates are used. The capsule is sutured, the trochanteric fragment is reduced anatomically and stabilized with two 3.5-mm cortical screws, the piriformis and triceps coxae muscles are sutured, and a layered closure is performed. ALTERNATIVES: The Kocher-Langenbeck approach might be used instead. RATIONALE: Surgical hip dislocation facilitates assessment of cartilage damage at the acetabulum, marginal impaction, labral tears and femoral head lesions, removal or reinsertion of free intra-articular fracture fragments, direct visualization of the accuracy of reduction, and verification of extra-articular screw placement.

Open Reduction and Internal Fixation of Acetabular Fractures Using the Modified Stoppa Approach.

BACKGROUND: The modified Stoppa approach is performed for safe and efficient management of acetabular fractures involving the anterior column. This approach avoids dissection of the inguinal canal, the femoral nerve, and the external iliac vessels as seen in the "second window" of the ilioinguinal approach and has thus been shown to be less invasive than the ilioinguinal approach1. As an intrapelvic approach, it facilitates the management of medial displacement fracture patterns involving the quadrilateral plate and dome impaction that typically occur in the elderly2,3. The reduced morbidity of this approach is of particular relevance for elderly patients who must respond to the stresses of injury and surgery with diminished physiological reserves. DESCRIPTION: The specific surgical steps include preoperative planning, patient positioning and setup, a Pfannenstiel incision, superficial and deep dissection, development of the Retzius space and retraction of the bladder, exposure of the superior pubic ramus and iliopectineal eminence, dissection and ligation of a potential corona mortis, exposure of the obturator nerve and vessels, subperiosteal preparation of the pubic ramus with retraction of the external iliac vessels, subperiosteal exposure of the quadrilateral plate with detachment of the internal obturator muscle and exposure of the posterior column, assessment of residual displacement by fluoroscopic views, longitudinal soft-tissue or lateral skeletal traction (optional) for reduction of medial displacement of the femoral head, disimpaction of the acetabular dome fragment and grafting of the supra-acetabular void (optional) under fluoroscopic and arthroscopic (optional) control, and reduction and fixation of extra-articular components (iliac wing posteriorly and pubic ramus anteriorly), the posterior column (infra-acetabular screw), and the quadrilateral plate (buttress plate). Before wound closure, the urine output is checked for occurrence of hematuria, an indication of bladder penetration. The anterior lamina of the rectus sheath is then sutured, and a layered closure performed. ALTERNATIVES: The ilioinguinal approach might be used instead. RATIONALE: The modified Stoppa approach avoids dissection within the inguinal canal, the second window of the ilioinguinal approach. Therefore, this approach is less invasive and might be an alternative for joint-preserving surgery, especially in the elderly.

The Pararectus Approach: A New Concept.

BACKGROUND: Even 50 years after the introduction of the extrapelvic ilioinguinal approach for open reduction and internal fixation of acetabular fractures involving predominantly the anterior column, this approach is still acknowledged as being the so-called gold standard1. The pattern of acetabular fractures has changed within the last 10 to 20 years2,3, with a greater prevalence of quadrilateral plate fractures that is due in part to the increase in elderly trauma. The intrapelvic approach, also called the modified Stoppa approach4-6, was introduced as a less invasive alternative to the extrapelvic ilioinguinal approach, mostly combined with the first window of the ilioinguinal approach. The Pararectus approach also offers intrapelvic surgical access and has demonstrated safe surgical dissection with enhanced exposure and favorable outcome compared with the Stoppa approach7-10. DESCRIPTION: The skin incision runs along the lateral border of the rectus abdominis muscle to develop the anterior rectus sheath. The retroperitoneal space lateral to the rectus abdominis muscle is entered and the inferior epigastric vessels and the round ligament in females or the spermatic cord in males are identified. The superior pubic ramus and the iliopectineal eminence are exposed. If the corona mortis vessels (a vascular anastomosis between the obturator vessels and the external iliac artery) are present, they are ligated. The obturator nerve and vessels are exposed. The dissection is then directed posteriorly under retraction of the external iliac vessels with further subperiosteal exposure of the pubic ramus, the quadrilateral plate, and the posterior column. Any nonessential iliolumbar vessels are ligated. Residual displacement is assessed with fluoroscopic views. For reduction of a medially displaced femoral head, longitudinal extremity soft tissue or lateral skeletal traction (optional), with a Schanz pin in the greater trochanter, is used. For disimpaction of acetabular dome fragments and grafting of a supra-acetabular void (optional), a fluoroscopy unit is used to assess reduction and identify the void; in addition, arthroscopy can be used. The scope is introduced through the fracture gap to check for reduction without any water or specific setup. For reduction and fixation of extra-articular components (iliac wing posteriorly and superior pubic ramus anteriorly), the posterior column, and the quadrilateral plate, the fluoroscopy unit is used. The anterior lamina of the rectus sheath is sutured, and a layered closure performed. ALTERNATIVES: The ilioinguinal or modified Stoppa approach might be used instead. RATIONALE: The Pararectus approach combines the advantages of the ilioinguinal approach and the Stoppa approach. The Pararectus approach facilitates surgical access directly above the hip joint, which is comparable with the access obtained through the second window of the ilioinguinal approach, but without dissection of the inguinal canal. Moreover, the Pararectus approach provides intrapelvic visualization that is at least equivalent to that offered by the Stoppa approach but without losing any direct access to the hip joint.

Chondrocytes within osteochondral grafts are more resistant than osteoblasts to tissue culture at 37°C.

It is proposed that an ideal osteochondral allograft for cartilage repair consists of a devitalized bone but functional cartilage. The different modes of nutrient supply in vivo for bone (vascular support) and cartilage (diffusion) suggest that a modulation of storage conditions could differentially affect the respective cells, resulting in the proposed allograft. For this purpose, osteochondral tissues from porcine humeral heads were either cultured at 37°C for up to 24 hr or stored at 4°C for 24 hr, the temperature at which osteochondral allografts are routinely stored. Functionality of the cells was assessed by in situ hybridization for transcripts encoding collagen types I and II. At 37°C, a time-dependent significant reduction of the bone surface covered with functional cells was observed with only 5% ± 5% coverage left at 24 hr compared with 41% ± 10% at 0 hr. Similarly, cartilage area containing functional cells was significantly reduced from 84% ± 7% at 0 hr to 70% ± 3% after 24 hr. After 24 hr at 4°C, a significantly reduced amount of functional cells covering bone surfaces was observed (27% ± 5%) but not of cells within the cartilage (79% ± 8%). In the applied experimental setup, bone cells were more affected by tissue culture at 37°C than cartilage cells. Even though chondrocytes appear to be more sensitive to 37°C than to 4°C, the substantially reduced amount of functional bone cells at 37°C warrants further investigation of whether a preincubation of osteochondral allografts at 37°C--prior to regular storage at 4°C--might result in an optimized osteochondral allograft with devitalized bone but viable cartilage.

Hypoxic expansion promotes the chondrogenic potential of articular chondrocytes.

For cell-based cartilage repair strategies, an ex vivo expansion phase is required to obtain sufficient numbers of cells needed for therapy. Although recent reports demonstrated the central role of oxygen for the function and differentiation of chondrocytes, a beneficial effect of low oxygen concentrations during the expansion of the cells to further improve their chondrogenic capacity has not been investigated.Therefore, freshly harvested bovine articular chondrocytes were grown in two-dimensional monolayer cultures at 1.5% and 21% O2 and redifferentiation was subsequently induced in three-dimensional micromass cultures at 1.5%, 5%, and 21% O2. Cells expanded at 1.5% O2 were characterized by low citrate synthase (aerobic energy metabolism)--and high LDH (anaerobic energy metabolism-activities,suggesting an anaerobic energy metabolism. Collagen type II mRNA was twofold higher in cells expanded at 1.5% as compared to expansion at 21% O2. Micromass cultures grown at 21% O2 showed up to a twofold increase in the tissue content of glycosaminoglycans when formed with cells expanded at 1.5% instead of 21% O2. However, no differences in the levels of transcripts and in the staining for collagen type II protein were observed in these micromass cultures. Hypoxia (1.5% and 5% O2) applied during micromass cultures gave rise to tissues with low contents of glycosaminoglycans only. In vivo, the chondrocytes are adapted to a hypoxic environment. Taking this into account, by applying 1.5% O2 in the expansion phase in the course of cell-based cartilage repair strategies, may result in a repair tissue with higher quality by increasing the content of glycosaminoglycans.