Error of intraoperative measurement of stem anteversion is decreased by measuring in neutral hip position during total hip arthroplasty.

BACKGROUND: Intraoperative stem anteversion, which is the angle between the lower leg axis and the trial-stem axis with hip flexion and adduction, is generally evaluated by the surgeon's visual estimation during total hip arthroplasty (THA). However, the conventional approach can be influenced by knee osteoarthritis or uncertain surgeon's observation point. Therefore, we developed a new method for measuring the stem anteversion angle in the neutral hip position using an original rod attached to the trial-stem perpendicular to the long axis and parallel to the stem neck. This study aimed to assess the accuracy of our method in comparison with the conventional method of measuring intraoperative stem anteversion angle. METHODS: We measured the intraoperative stem anteversion angle in consecutive 106 hips of 106 patients who underwent cementless primary THA with a tapered wedge stem. Absolute error in the stem anteversion angle was expressed as the difference between intraoperative (common vs. neutral hip positions) and postoperative computed tomography measurements, i.e., true stem anteversion. Additionally, we investigated the factors affecting these errors. RESULTS: The absolute error of measurement was significantly smaller in the neutral hip position than in the common position (3.0° ± 2.5° vs. 8.0° ± 3.9°; p < 0.0001). The factor associated with the error was advanced knee osteoarthritis in the common position, whereas it was not statistically significant in the neutral hip position. CONCLUSIONS: This study suggests that the error in the intraoperative measurement of stem anteversion is decreased by measuring in the neutral hip position during THA.

Computer simulation based on in vivo kinematics of a replaced hip during chair-rising for elucidating target cup and stem positioning with a safety range of hip rotation.

Background After total hip arthroplasty, dislocation can occur when a patient unexpectedly assumes internal/external limb positions, even during chair-rising, which is a frequently activity of daily life. Therefore, determining the target cup position to avoid impingement in unexpected limb positions using in vivo data of daily life activities is critical. Methods A computer simulation was performed on 21 total hip arthroplasty patients using patient-specific component placements and hip kinematics obtained during chair-rising analysis using image-matching techniques. The liner-to-neck distance and impingement were evaluated by simulating the change in internal/external rotation angle at maximum hip flexion/extension from 0 to 90°. The cutoff values of cup anteversion and combined anteversion at 60° of internal/external rotation were determined. Findings The anterior/posterior liner-to-neck distances were negatively correlated with internal/external rotation angles (r = -0.82 and -0.78, respectively) and decreased by 1.7 and 1.8 mm for every 15° increase, respectively. Three cases (14%) of anterior/posterior impingement were observed at 60° of internal/external rotation angle, respectively. The cutoff values for cup anteversion and combined anteversion to avoid impingement at 60° of internal/external rotation angle were 12°-25°/38°-62°, respectively. The stem anteversion, adjustable by cup anteversion to meet both the target cup anteversion and combined anteversion, was 13°-50°. Interpretation Simulated unintentional internal or external hip rotation, even during chair-rising, caused impingement and posed a dislocation risk. If the stem anteversion is excessively small or large in meeting the target combined anteversion, adjustments to stem anteversion could be recommended in addition to adjustments in cup anteversion.

How does transtrochanteric anterior rotational osteotomy change the dynamic three-dimensional intact ratio in hips with osteonecrosis of the femoral head?

BACKGROUND: The intact ratio (the ratio of the intact area of the femoral head) on a two-dimensional anteroposterior radiograph is associated with the prognosis of hips with osteonecrosis of the femoral head after transtrochanteric anterior rotational osteotomy. However, changes of the three-dimensional intact ratio during dynamic weight-bearing activity and correlation of the three-dimensional intact ratio with clinical scores are still unknown. METHODS: Kinematics of eight hips with osteonecrosis of the femoral head that underwent anterior rotational osteotomy were analyzed using image-matching techniques during chair-rising and squatting preoperatively and postoperatively. Two types of dynamic three-dimensional intact ratios were examined, including the lunate covered area (IRLC) and in vivo peak contact force vector intersected area (IRFV). The static three-dimensional intact ratio in each octant of the femoral head was also examined. FINDINGS: The mean Harris hip score significantly improved from 67 preoperatively to 90 postoperatively. During chair-rising rising/squatting, the mean IRLC and IRFV significantly increased from 42%/41% and 7%/4% preoperatively, to 66%/65% and 79%/77% postoperatively, respectively. IRLC significantly changed during the motion whereas substantial postoperative IRFV was maintained throughout the motion. Additionally, Harris hip score and the static three-dimensional intact ratio in the superolateral regions had significant positive correlations with both IRLC and IRFV. INTERPRETATION: Hip kinematics affected IRLC but not IRFV, which suggests that substantial intact bone occupies the region in which peak contact forces are applied during deep hip flexion. Additionally, improving intact ratio in the superolateral region led to improvements in both IRLC and IRFV with favorable clinical scores.

Total hip arthroplasty after periacetabular osteotomy versus primary total hip arthroplasty: a propensity-matched cohort study.

BACKGROUND: Controversy still exist regarding the outcomes of total hip arthroplasty (THA) after periacetabular osteotomy (PAO). The purpose of this study was to compare the clinical and radiologic outcomes of THA after PAO with primary THA based on balanced baseline characteristics with propensity score matching. METHODS: Using propensity score matching, 1:2 matched cohort to facilitate comparison between patients who underwent primary cementless THA with or without previous PAO. Then, we compared the operative time, blood loss, complications, postoperative clinical score, cup size, position, and alignment of acetabular cup, and degree of bony coverage on cup between the two groups. RESULTS: Thirty-five patients with 37 hips who underwent THA after PAO were successfully matched to 70 patients with 74 hips who underwent primary THA. The operative time and blood loss in THA after PAO were significantly longer and larger than those in primary THA (P < 0.001 and = 0.0067, respectively). Clinical score showed no difference between the groups (P > 0.05). For THA after PAO, the cup size and bony coverage were larger (P = 0.0014 and < 0.001, respectively), and the hip center was significantly higher and laterally (P < 0.001 and < 0.001, respectively) comparing primary THA. CONCLUSION: This study demonstrated longer operative time and larger blood loss without difference in the postoperative clinical score or complications between THA after PAO and primary THA. Furthermore, THA after PAO provided larger cup size and superolaterally positioned cup center without difference in the cup inclination or anteversion comparing primary THA.

Is lateral acetabular rotation sufficient to correct anterolateral deficiency in periacetabular reorientation osteotomy? A CT-Based simulation study.

BACKGROUND: Residual acetabular deficiency after periacetabular reorientation osteotomy can result in suboptimal outcome. The optimal algorithm of acetabular fragment correction to achieve normal anterolateral acetabular coverage is not well characterized. The aim of this study was to determine the prevalence of residual anterolateral deficiency after lateral acetabular rotation and to evaluate the ability of additional sagittal and axial rotation of the acetabulum to normalize the acetabular coverage in periacetabular osteotomy. METHODS: We performed computed tomography-based simulated periacetabular osteotomy on 85 patients (85 hips) with hip dysplasia. The acetabular fragment was rotated laterally to achieve a lateral center-edge angle (CEA) of 30°. For hips with residual anterolateral deficiency, which were identified based on the reference interval of the anterior CEA, the acetabulum was further rotated in the sagittal or axial direction in 5-degree increments from 5° to 20°, and the ability of these two manoeuvres to restore a normal anterior CEA was assessed. RESULTS: After lateral acetabular rotation, 16 hips (19%) had residual anterolateral deficiency, 67 hips (79%) had normal acetabular coverage, and 2 hips (2.4%) had acetabular overcoverage. A preoperative anterior CEA <37° predicted residual deficiency (sensitivity, 94%; specificity, 81%). Additional anterior sagittal rotation was more effective than posterior axial rotation in normalizing the anterior CEA, while minimizing the decrease in posterior CEA. The highest number of hips with normal anterior and posterior CEA was noted at 10° sagittal rotation (81%), which was followed by 15° sagittal rotation (63%). CONCLUSIONS: Normal anterolateral coverage was achieved in 79% of patients after rotating the acetabulum laterally. However, lateral rotation of the acetabulum may be insufficient to correct the anterolateral deficiency in patients with an anterior CEA of <37°. In them, additional 10°-15° anterior sagittal rotation may be appropriate to achieve sufficient anterolateral coverage while retaining posterolateral coverage.

Dynamic hip kinematics before and after periacetabular osteotomy in patients with dysplasia.

BACKGROUND: We prospectively analyzed the hip kinematics in patients with developmental dysplasia of the hip (DDH) before and after periacetabular osteotomy (PAO) and in healthy subjects while squatting to determine the influence of coverage of the femoral head on hip kinematics. METHODS: 14 hips in 14 patients with DDH and 10 hips in 10 volunteers were included. Continuous radiographs while squatting and computed tomography images were obtained to assess the in vivo kinematics of the hip and the rim-neck distance using density-based 3D-to-2D model-to-image registration techniques. RESULTS: The maximum hip flexion angles were 100.4° and 94.9° before and after PAO (p = 0.0863), respectively. The maximum hip flexion angles after PAO did not significantly differ from those of normal hips (102.2°; p = 0.2552). The hip abduction angles at maximum hip flexion were 31.7° and 26.2° before and after PAO (p = 0.1256), respectively. The rim-neck distance decreased from averaged 12.2 mm-8.9 mm (p = 0.0044) after PAO. The lateral center edge angle (LCEA) and anterior center edge angle (ACEA) significantly improved 14.7°-42.4° and 50.4°-54.0° after PAO (p < 0.0001, p = 0.0347), respectively; in particular, the ACEA after PAO did not significantly differ from that in the normal hips (p = 0.1917). The ACEA was not correlated with hip flexion, or the rim-neck distance (p = 0.9601, 0.8764). The LCEA was also not correlated with hip abduction (p = 0.1683). CONCLUSION: Patients after PAO showed no significant difference in maximum hip flexion while squatting compared to before PAO and normal hips. Horizontalized weight-bearing acetabulum with normalized ACEA could be adequate correction of the acetabular fragment to restore hip RoM without coxalgia that induce the inability to perform squats after PAO.

In vivo kinematics, component alignment and hardware variables influence on the liner-to-neck clearance during chair-rising after total hip arthroplasty.

BACKGROUND: There is an interest in quantifying dynamic hip kinematics before and after total hip arthroplasty (THA) during chair-rising: one of daily life activities. METHODS: The study consisted of 21 patients who underwent unilateral total hip arthroplasty for symptomatic osteoarthritis. We obtained continuous radiographs using a flat-panel X-ray detector while the participants rose from chair. We assessed the pre and postoperative hip joint's movements using three-dimensional-to-two-dimensional model-to-image registration techniques. We also measured minimum liner-to-neck distances at maximum hip flexion and extension as anterior and posterior liner-to-neck distances, respectively. Multivariate analyses were applied to determine which factors were associated with liner-to-neck distances. RESULTS: The cup inclination, cup anteversion, and stem anteversion averaged 37.4°, 23.1°, and 30.1°, respectively. Significantly larger maximum hip flexion angle (72°) was found during chair-rising after THA compared to that before THA (63°, P < 0.01). The anterior pelvic tilt at the maximum hip flexion after THA (3° of anterior tilt) was significantly (P < 0.05) anterior compared to that before THA (1° of posterior tilt). The anterior and posterior liner-to-neck distances averaged 12.3 mm and 8.1 mm, respectively, with a significant difference (P < 0.01). No liner-to-neck contact was found in any hips. In multivariate analysis, the hip flexion angle, cup inclination, stem anteversion and head diameter were significantly associated with the anterior liner-to-neck distance (P < 0.05), the hip extension angle, cup anteversion, neck length and with or without elevated rim were significantly associated with the posterior liner-to-neck distance (P < 0.05, 0.01, 0.05, 0.01, respectively). CONCLUSION: This study indicates that well-positioned THA provide increased range of hip flexion with sufficient anterior liner-to-neck clearance during chair-rising. Dynamic hip kinematics, component position, and hardware variables significantly influenced on the liner-to-neck clearance under weight-bearing conditions.

In vivo kinematic analysis of replaced hip during stationary cycling and computer simulation of optimal cup positioning against prosthetic impingement.

BACKGROUND: Dynamic hip kinematics during stationary cycling after total hip arthroplasty (THA) have been unclear. Furthermore, no computer simulation of optimal cup position based on in vivo kinematics has yet been assessed. METHODS: This study consisted of 7 patients who underwent unilateral primary THA for symptomatic osteoarthritis. Using a flat-panel X-ray detector, continuous radiographs were obtained during stationary cycling. We analyzed the three-dimensional replaced hip kinematics from the top to the bottom position of the crank using image-matching techniques and quantified minimum liner-to-stem neck distance. Simulation analyses with in vivo kinematics were performed to examine patient-specific optimal cup placement against prosthetic impingement. FINDINGS: During stationary cycling, pelvis showed 27.1° of posterior tilt on average without significant change. Hip flexed by 59.4° and 19.3° on average at the top and bottom positions, respectively. Minimum liner-to-neck distance was 8.8 mm on average at the bottom position. Liner-to-neck, bone-to-bone, or bone-to-component impingement was not observed at any positions in any hips. Simulation analysis of cup placement showed that larger cup anteversion, inclination, and use of elevated liner significantly decreased the minimum distance between posterior liner and stem neck. Cup anteversion of more than 30° with elevated liner could cause posterior liner-to-neck impingement at bottom position. INTERPRETATION: Stationary cycling after THA provides no excessive hip range of motion or liner-to-neck contact. Cup placement and use of elevated liner significantly influence the minimum liner-to-neck distance, in some cases simulating posterior prosthetic impingement.

Dynamic hip kinematics during recreational classical ballet and hula dance after total hip arthroplasty: two case reports.

BACKGROUND: The in vivo assessment of the three-dimensional kinematics of the hip during dance activities in patients after total hip arthroplasty has not been previously reported. We evaluated the replaced hip kinematics during recreational classical ballet and hula dance using radiographic-based image-matching techniques. CASE PRESENTATION: A 58-year-old Japanese woman (patient 1; height, 157 cm; weight, 74.5 kg) and a 73-year-old Japanese woman (patient 2; height, 153 cm; weight, 48 kg) were still doing classical ballet and hula dance, respectively, after primary total hip arthroplasty. For ballet, there were gradual three-dimensional hip movements with 48° flexion, 36° abduction, and 49° external rotation in développé and 34° flexion, 29° abduction, and 43° external rotation in plié. For hula, there were small three-dimensional hip movements with 31° flexion, 15° adduction, and 11° external rotation in kao and 17° flexion, 11° adduction, and 11° external rotation in kaholo. No liner-to-neck contact was found in any dance activities. CONCLUSION: Both classical ballet and hula dance produced complex ranges of hip movements and activity-dependent kinematics. These kinematic data could be useful for recommending each patient with total hip arthroplasty to continue recreational dance activities.

Does high hip centre affect dislocation after total hip arthroplasty for developmental dysplasia of the hip?

BACKGROUND: To achieve sufficient socket coverage by the native bone, high placement of cementless acetabular cup is often required. We previously reported, using computer simulation, that higher hip centre improved the bone coverage but decreased the range of motion in total hip arthroplasty (THA) for patients with hip dysplasia. However, in a clinical setting, the correlation between the hip centre height and dislocation after primary THA is still unclear. We examined whether a high hip centre affects dislocation after THA. METHODS: A total of 910 patients, with 1079 dysplastic hips, who underwent primary THA were retrospectively reviewed. The age at THA averaged 63.0 years and mean follow-up was 74.3 months. Vertical centre of rotation (V-COR) was defined as the distance from the head centre to the interteardrop line. Uni- and multivariate logistic regression models were applied to identify significant factors affecting dislocation. RESULTS: Ten hips in nine patients (0.9%) had dislocation after THA. In univariate analysis, age at surgery and V-COR were significant risk factors for dislocation. Multivariate analysis identified advanced age at operation (odds ratio [OR] 1.8/5 years), Crowe classification (OR 15.6), V-COR (OR 3.1/5 mm), and femoral head size (OR 11.6) as independent risk factors for dislocation. Receiver operating characteristic curve analysis revealed the cutoff value of the V-COR for dislocation as 23.9 mm. CONCLUSIONS: A higher hip centre with the V-COR > 23.9 mm affected dislocation after THA for DDH. Our results would be useful for reconstruction of the hip centre, particularly with cementless acetabular cups.

How does anteroposterior cup placement affect bone coverage and range of motion in primary total hip arthroplasty for hip dysplasia?

BACKGROUND: Due to anterior bone defects, high and/or posterior placement of an acetabular cup is often required to achieve sufficient coverage in patients with hip dysplasia. We examined whether posterior cup placement affected the postoperative range of motion (ROM) in primary total hip arthroplasty (THA). METHODS: Using computer software, bone coverage and ROM were examined in 32 patients with unilateral osteoarthritis of the hip with Crowe type II or III hip dysplasia. We determined the cup position to satisfy cup center-edge (Cup-CE) angle ≥0° and the required ROM. The cup was placed at the anatomic hip center and moved in 2-mm increments anteroposteriorly and 10-mm increments vertically. RESULTS: At vertical anatomic hip center, less than 68.8% hips fulfilled Cup-CE ≥0° regardless of anteroposterior position. Significantly more hips at higher hip center with posterior cup placement achieved Cup-CE ≥0° than hips at vertical anatomic hip center, and 10 mm higher hip center was the most suitable for achieving bone coverage. However, posterior and superior cup placement significantly decreased the flexion and IR due to early bone impingement, whereas ER and extension were not affected. A smoothing spline curve demonstrated that more posterior cup placement than 4.8 mm and 3.6 mm did not satisfy the required ROM at 10 mm and 20 mm higher hip center, respectively. CONCLUSIONS: Posterosuperior cup placement gained more bone coverage but decreased the range of hip flexion and internal rotation. Consequently, posterosuperior cup placement did not satisfy the required ROM.

Dynamic hip kinematics during squatting before and after total hip arthroplasty.

BACKGROUND: The difference in in vivo kinematics before and after total hip arthroplasty (THA) for the same subjects and the clearance between the liner and neck during squatting have been unclear. The purpose of the present study was to clarify (1) the changes in the in vivo kinematics between prosthetic hips and osteoarthritis hips of the same subjects and (2) the extent of the liner-to-neck clearance during squatting under weight-bearing conditions. METHODS: This study consisted of 10 patients who underwent unilateral THA for symptomatic osteoarthritis. Using a flat-panel X-ray detector, we obtained continuous radiographs during squatting. We analyzed the hip joint's movements using three-dimensional-to-two-dimensional model-to-image registration techniques. We also quantified the minimum distance at maximum flexion and extension, and the minimum angle at maximum flexion between the liner and stem neck. RESULTS: The maximum hip flexion angles post-THA (80.7° [range, 69.4-98.6°]) changed significantly compared with the pre-THA values (71.7° [range, 55.2°-91.2°]). The pelvic tilt angle (posterior +, anterior-) at the maximum hip flexion post-THA (10.4° [range, - 6.7° to 26.9°]) was significantly smaller than that at pre-THA (16.6° [range, - 3° to 40.3°]). The minimum anterior and posterior liner-to-neck distances averaged 10.9 and 8.0 mm, respectively, which was a significant difference. The minimum liner-to-neck angle at maximum flexion averaged 34.7° (range, 20.7°-46.3°). No liner-to-neck contact occurred in any of the hips. CONCLUSION: THA increased the range of hip joint motion and the pelvis tilted anteriorly more after than before THA, with sufficient liner-to-neck clearance during squatting. These data may be beneficial for advising patients after THA regarding postoperative activity restrictions in daily life.

Sports Participation in Patients After Total Hip Arthroplasty vs Periacetabular Osteotomy: A Propensity Score-Matched Asian Cohort Study.

BACKGROUND: No studies have compared sports participation between total hip arthroplasty (THA) and periacetabular osteotomy (PAO) in matched Asian cohorts. We investigated sports participation and activity levels in Asian THA cohort, and compared them between THA and PAO cohorts. METHODS: Multivariate analyses were applied to determine which factors were associated with postoperative sports participation and University of California-Los Angeles (UCLA) activity score in (1) 524 THA patients and (2) 487 acetabular dysplasia patients (295 THA patients and 192 PAO patients). In addition, postoperative sports participation and UCLA score were compared between 62 THA and 62 PAO patients after adjusting for baseline characteristics with propensity score matching. RESULTS: Sports participation and UCLA score significantly increased after THA (P < .001 in both analyses). Preoperative sports participation was the factor most associated with both postoperative sports participation and UCLA score in both 524 THA patients and 487 acetabular dysplasia patients (P < .001 in all analyses). Multivariate analysis in 487 acetabular dysplasia patients demonstrated that THA, compared with PAO, was negatively associated with postoperative sports participation (P < .001), but not postoperative UCLA score (P = .22). THA patients showed significantly lower rate of postoperative sports participation (32.3% and 51.6%, respectively, P = .046), but not postoperative UCLA score (5.0 ± 1.6 and 5.2 ± 1.9, respectively, P = .47) compared with matched PAO patients. CONCLUSION: THA significantly increased both sports participation and activity levels. Both multivariate and propensity score-matched analyses showed that postoperative activity levels were comparable between THA and PAO cohorts.

Does Participation in Sports Affect Osteoarthritic Progression After Periacetabular Osteotomy?

BACKGROUND: Periacetabular osteotomy (PAO) is an effective treatment for symptomatic acetabular dysplasia. However, whether postoperative participation in sports leads to progression of the Kellgren-Lawrence (KL) grade of osteoarthritis (OA) in these patients is unclear. PURPOSE: To investigate (1) participation in sports before and after PAO and (2) whether postoperative participation in sports leads to progression of the KL grade. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The authors retrospectively reviewed data on 161 patients (183 hips) who underwent PAO for symptomatic acetabular dysplasia with preoperative KL grade 1 or 2 between 1998 and 2011. The mean age at the time of surgery was 42.0 ± 10.9 years (range, 12-64 years), and the mean follow-up duration was 100 months (range, 13-180 months). Data included participation in sports, the University of California, Los Angeles (UCLA) activity scale score, age at the time of surgery, body mass index, follow-up duration, history of treatment for developmental hip dislocations, Merle d'Aubigné-Postel score, Oxford Hip Score, center-edge angle, and KL grade. Univariate and multivariate analyses were applied to determine which factors were associated with progression to KL grade 3 or 4 after PAO. RESULTS: The number of patients who participated in sports significantly increased from 50 (31.1%) preoperatively to 89 (55.3%) postoperatively. The mean UCLA score significantly increased from 4.7 ± 2.1 preoperatively to 5.5 ± 2.0 postoperatively. The KL grade progressed to grade 3 or 4 in 16 hips, including 4 hips that underwent conversion to total hip arthroplasty. No significant differences were found in postoperative participation in sports (89 hips [53.3%] vs 11 hips [68.8%], respectively; P = .24) and the UCLA score (5.6 ± 2.0 vs 5.1 ± 2.0, respectively; P = .30) between hips with KL grade 1 or 2 and KL grade 3 or 4. A multivariate analysis revealed that no factors, including postoperative participation in sports, were significantly associated with progression to KL grade 3 or 4. CONCLUSION: Postoperative participation in sports after PAO did not significantly and negatively influence progression of the KL grade at midterm follow-up.

Does High Hip Center Decrease Range of Motion in Total Hip Arthroplasty? A Computer Simulation Study.

BACKGROUND: High placement of a cementless acetabular cup is often required to have sufficient bone coverage in hip dysplasia. We examined whether a high hip center decreases the postoperative range of motion (ROM) in total hip arthroplasty. METHODS: Using a computer software, ROM and bone coverage were examined in 32 patients with unilateral osteoarthritis of the hip with Crowe type II or III hip dysplasia. The cup was placed at the anatomic hip center and moved vertically in 5-mm increments. Vertical center of rotation (V-COR) was defined as the distance from the head center to the interteardrop line. The required ROM was defined as flexion ≥110°, internal rotation (IR) at 90° flexion ≥30°, extension ≥30°, and external rotation ≥30°. We determined the V-COR to satisfy the required ROM and cup center-edge angle (Cup-CE) ≥0°. RESULTS: Only 40.6% of the patients satisfied Cup-CE ≥0° at the anatomic hip center. Bone coverage increased with the peak at 30, 35 mm of V-COR (90.6% satisfied Cup-CE ≥0°) and decreased at ≥40 mm. Higher V-COR resulted in lower range of flexion and IR, but increased the range of extension and external rotation. The cutoff value from the receiver-operating characteristic curve for both flexion and IR was a V-COR of 35 mm. CONCLUSION: The higher hip center gained more bone coverage but decreased the range of hip flexion and IR. Acceptable V-COR in hip dysplasia was around 35 mm, about 20 mm above the true hip center, in terms of ROM.

The Absence of Hydroxyapatite Coating on Cementless Acetabular Components Does Not Affect Long-Term Survivorship in Total Hip Arthroplasty.

BACKGROUND: Hydroxyapatite (HA) has been applied to joint prostheses as a bioactive coating to prolong their durability. However, HA benefits for cup survival in total hip arthroplasty (THA) remain controversial. In this study, we compared the survival of cups with and without HA coating during a minimum follow-up of 18 years. METHODS: In total, 183 THA cases in 163 patients were analyzed, including 73 cups with HA coating (HA(+) group) and 110 without HA coating (HA(-) group); otherwise, the cups had identical titanium-sprayed rough surfaces and were fixed with screws. In both groups, the same conventional polyethylene liners were applied. Zirconia and alumina ceramic heads were used in the HA(+) and HA(-) groups, respectively. We retrospectively analyzed cup survival based on cup revision for any reason or aseptic loosening as end points. RESULTS: In total, 7 and 8 revisions were performed in the HA(-) and HA(+) groups with survival rates of 86.3% and 90.1%, respectively. Among them, 3 cups in the HA(-) group and 1 cup in the HA(+) group were revised for aseptic loosening in 20 years (survival rates 94.1% and 98.7%, respectively). No significant difference was detected in cup survival rates between the groups based on both end points. There were no stem revisions during the observation period. CONCLUSION: The results suggested that HA coating did not have either beneficial or adverse effects on the long-term cup survival in primary cementless THA.

Recurrent dislocations of the atlantooccipital and atlantoaxial joints in a halo vest fixator are resolved by backrest elevation in an elevation angle-dependent manner.

BACKGROUND CONTEXT: Halo fixation is now universally performed in the initial reduction and fixation of unstable upper cervical spine injuries; however, persistent high instability and recurrent dislocations of the atlantooccipital and atlantoaxial joints after fixation are not well recognized. PURPOSE: The aim was to describe persistent instability of traumatic dislocations of the atlantooccipital and atlantoaxial joints after halo fixation and a useful method for preventing instability. STUDY DESIGN: This was a case report of a patient who survived traumatic dislocations of the atlantooccipital and atlantoaxial joints. PATIENT SAMPLE: A 73-year-old woman diagnosed with dislocations of the atlantooccipital and atlantoaxial joints along with multiple other injuries sustained in a traffic accident was included. METHODS: After initial closed reduction and halo fixation, congruity of the atlantooccipital and atlantoaxial joints was evaluated using, condylar gap, atlantodental interval, and flexion angulation of C1-C2 after the initial examination and before surgery. RESULTS: Changes in parameters 12 hours after halo fixation revealed re-dislocations and instability of the joints. Backrest elevation with halo fixation tended to reduce re-dislocations. Therefore, we carefully increased the backrest angle and measured the parameters at several angles of elevation within a range that did not affect vital signs to observe the effectiveness of elevation against re-dislocations. Elevation changed the parameters in an elevation angle-dependent manner, and these changes suggested that elevation was effective for reducing re-dislocation of both the atlantooccipital and atlantoaxial joints during halo fixation. With no major complications, this method enabled us to maintain good congruity of the joints for approximately 2 weeks until posterior spinal fusion with internal fixation. CONCLUSIONS: Backrest elevation with halo fixation appears safe to be performed without any other devices and is beneficial for blocking re-dislocation of both the atlantooccipital and atlantoaxial joints as well as possible secondary damage to the upper cervical spinal cord during the external fixation period.