High incidence of femoroacetabular impingement deformity in bi-column acetabular fractures.

INTRODUCTION: Dynamic interaction of cam and pincer deformities can result in pathological contact forces in femoroacetabular impingement (FAI) syndrome. Similar deformities were noted during acetabular fracture reconstruction. We hypothesise that the prevalence of FAI deformity is higher in patients sustaining acetabular fractures than in a control group. METHODS: This retrospective radiographic study compared the parameters that define FAI deformity in 100 patients consecutively admitted to a trauma unit with an acetabular fracture and a control group of 100 patients with lateral compression pelvic fracture without acetabular injury. Both underwent identical clinical imaging. Centre-edge angles (CEA) and alpha angles were used to define patients with pincer, cam, or mixed FAI deformity. RESULTS: There were significantly more patients with FAI deformity in the acetabular fracture group than in the control group (71% vs. 18%, p < 0.0001). There were considerably more fractures involving both anterior and posterior acetabular columns in patients with 'pincer' sockets (p = 0.02, OR = 2.95, 95% CI, 1.12-7.78). CONCLUSIONS: There is a high prevalence of cam and pincer deformities in patients with acetabular fractures, particularly bi-column fractures.

The posterior acetabular wall (PAW): an aid to acetabular orientation at primary THA.

INTRODUCTION: Incorrect acetabular component positioning during total hip arthroplasty (THA) may lead to dislocation, impingement, wear and revision. Surgeons commonly use the transverse acetabular ligament (TAL) as a landmark for acetabular component orientation. The posterior acetabular wall (PAW) is a structure easily viewed on plain radiography and its position can help guide acetabular component position. In this study, we examine the efficacy of preoperative radiographs in predicting cup position relative to the PAW. METHODS: Prospective data was recorded on radiographic findings of the posterior wall (prominent, normal, deficient) on a consecutive series of 200 primary THAs utilising a standardised posterior approach. The final cup position relative to the wall was recorded (prominent, flush, deep). Cup inclination and version were then assessed by postoperative radiography and any instances of dislocation recorded. RESULTS: There were 117 females and 83 males with a mean age of 66.5 years. 154 were recorded as having a normal PAW on radiographs, 152 had the cup positioned in line with the TAL and flush to the PAW. 29 had a deficient PAW and 27 of these had a cup positioned prominently with 17 having a prominent PAW and of these 16 a deep cup position. Postoperative radiographs showed a mean cup version of 20.8° and inclination of 44.7° using this method. There were 21 outliers (10.5%) with no dislocations at a minimum 12-month follow-up. CONCLUSIONS: The TAL is a continuation of the posterior labrum. As such, the posterior wall is a useful adjunct to and surrogate landmark for the TAL. It has the added advantage that it is visible on radiographs and so aids surgical planning with respect to cup positioning.

Novel use of a trabecular metal spacer in the treatment of a long-standing ulnar fracture non-union.

The use of trabecular metal (TM) implants in spine and joint surgery is well documented. However, their use has yet to be reported as an alternative to either allograft or autograft in the management of fracture non-unions. We present our experience in using a TM implant for treating a patient with a long-standing ulnar fracture non-union. Excision of devitalised bone resulted in a 17 mm defect which the TM implant was used to infill. The defect was then bridged with a locking plate. At 2-year clinical and radiographic review, bony union and a pain-free return to full function was noted. In this case, the use of a TM implant avoided the morbidity associated with an iliac crest autograft.

Hip resurfacing arthroplasty in patients with varus deformity of the femoral neck-shaft angle.

Hip resurfacing arthroplasty (HRA) in patients with a varus deformity of the femoral neck-shaft angle (NSA) is associated with poorer outcomes. Our experience has not reflected this. We examined the Oxford Hip Scores (OHS), Harris Hip Scores (HHS) and outcomes of patients with varus hips against a normal cohort to ascertain any significant difference. We identified 179 patients. Measurement of the femoral neck-shaft angle was undertaken from antero-posterior radiographs pre-operatively. The mean NSA was 128.5 degrees (SD 6.3). Patients with a NSA of less than 122.2 were deemed varus and those above 134.8 valgus. These parameters were consistent with published anatomical studies. The 'varus' cohort consisted of 23 patients, mean NSA 118.7 (range 113.6-121.5), mean follow-up 49 months (range 13-74). Mean OHS and HHS were 16 and 93.5 respectively. Complications included 2 cases of trochanteric non-union, but there were no femoral neck fractures, early failures or revisions. The 'normal' cohort consisted of 125 patients, mean NSA 128 degrees, mean follow-up 41 months (range 6-76). The OHS and HSS were 18.8 and 88.9 respectively. Complications included 5 trochanteric non-unions and 1 revision due to an acetabular fracture following a fall. Statistical analysis demonstrated no statistical difference between the cohorts' OHS (p=0.583) or HHS (p=0.139). Our experience in patients with a varus femoral neck has been positive. We have not yet experienced any femoral neck fractures, which we believe is in part due to the use of an uncemented femoral component and preservation of blood supply.

Femoroacetabular impingement and classification of the cam deformity: the reference interval in normal hips.

BACKGROUND AND PURPOSE: Most patients with femoroacetabular impingement (FAI) have a cam deformity, which may be quantified by measuring the alpha angle and anterior offset ratio (AOR). Knowledge of what constitutes a "normal" alpha angle and AOR is limited. We defined the reference intervals of these measurements from normal hips in the general population. PATIENTS AND METHODS: 157 individuals from the general population were reviewed clinically and radiographically. 74 individuals with clinical evidence of hip disease or radiographic evidence of osteoarthritis (OA) were excluded, leaving a study group of 83 individuals (mean age 46 (22-69) years, 44 females) with normal hips. The alpha angles and AORs were measured from cross-table lateral radiographs taken in 15 degrees internal rotation. A validation study consisting of a cadaver study and a measurement reliability study was also performed. RESULTS: The mean alpha angle was 48 degrees in men and 47 degrees in women. The mean AOR was 0.19, the same in men and women. Thus, sexes were combined to derive 95% confidence intervals for the population mean alpha angle (46-49 degrees ) and AOR (0.18-0.20). The 95% reference interval for the alpha angle was 32-62 degrees degrees, and for the AOR it was 0.14-0.24. The validation study confirmed that these measurements were resistant to a reasonable degree of variation in positioning and that the repeatability and reproducibility of the measurements was good. INTERPRETATION: These reference intervals indicate that clinically and radiographically normal hips may have alpha angles and AORs that have previously been considered "abnormal". The thresholds provided by this study will aid classification of individuals involved in longitudinal studies of FAI and OA, and may be of use to the practicing clinician in evaluating the young adult with hip pain.

Non-union following bilateral simultaneos Ganz trochanteric osteotomy.

Between January 2003 and December 2004, 13 patients underwent bilateral resurfacing arthroplasty via a Ganz trochanteric osteotomy. This bilateral group was mobilised fully weight-bearing with crutches. During the same period 139 Ganz trochanteric osteotomies were performed for unilateral hip resurfacing. These patients were mobilised with crutches, weight-bearing up to 10 kg on the operated leg. Nine osteotomies (32%) in the bilateral group subsequently developed a symptomatic non-union requiring revision of fixation. This compares with 10 patients (7%) in the unilateral group. Applying the Fisher's exact test, the difference reached significance (P=0.0004). In two patients a second revision was required to achieve union. In one patient, revision of trochanteric fixation precipitated a deep infection. Protected weight-bearing following a Ganz trochanteric osteotomy is important to the success of the procedure. Simultaneous bilateral hip arthroplasty through a Ganz approach should be avoided. If it is undertaken, we recommend that patients should be non weight-bearing for 6 weeks following surgery. Non-union following a Ganz trochanteric osteotomy for arthroplasty carries a significant morbidity.

Early failure of the Dual coat Cormet 2000 metal on metal acetabular component.

We report a 10% failure rate for aseptic loosening and overall revision rate of 15% at 5 years mean follow up in 190 patients using the Cormet 2000 Dual coat acetabular component. Between 2001 and 2004, the original Dual coat component was used in our region by 4 experienced arthroplasty surgeons. 142 were used with resurfacing heads. The average age was 54 and 99 were male. Revision for aseptic loosening was required in 20 cups (10%) at a mean interval of 23 months including five within 2 months. Persistent groin pain was seen in a further three patients who have declined further surgery. Failure of the backing of this implant to integrate reliably with bone has led to an unacceptably high early loosening rate of the original design which was phased out in 2003.

Acetabular component revision with frozen massive structural pelvic allograft: average 5-year follow-up.

We evaluated the use of a hemipelvic acetabular transplant in 20 revision hip arthroplasties with massive acetabular bone defects. We report 65% good intermediate-term results at a mean follow-up of 5 years (4-10 years). A cemented cup (without a reinforcement ring) was entirely supported by the allograft in all procedures. There were 7 failures (5 aseptic loosening and 2 deep infections). Two dislocations occurred but did not require acetabular revision. There were 2 cases in which moderate acetabular migration occurred but then stabilised and did not progress. Thirteen of 20 acetabular reconstructions did not require revision. We believe that these are satisfactory intermediate-term results for massive acetabular defects too large for reconstruction with other standard techniques.