What's new in shoulder and elbow surgery

Acetabular rim length: an anatomical study to determine reasonable graft sizes for labral reconstruction

The purpose of this article is to determine normative values for the length of the acetabular rim and detect differences between gender, age, ethnicity, height and leg length. Six measurements were taken on the acetabular rim of 143 cadaveric skeleton specimens (286 acetabula) using a coordinate-measuring device: circumferential (excluding acetabular notch), anterior inferior iliac spine (AIIS)-anterior, AIIS-posterior, 12-3 o'clock, 12-9 o'clock and 11-5 o'clock. Museum specimen height data and leg length data from a previous study were recorded for 109 of 143 specimens. Intraclass correlation coefficients were calculated. Student t-tests compared mean values. Multiple regression analysis was used to determine the relationship between acetabular rim length and gender, age, ethnicity, height and leg length. The average acetabular rim length in males for circumferential, AIIS-anterior, AIIS-posterior, 12-3, 12-9 and 11-5 o'clock were 15.8, 4.2, 11.7, 4.9, 4.7 and 9.5 cm, respectively; and for females: 13.7, 3.7, 10.0, 4.3, 4.1 and 8.3 cm, respectively. Intraclass correlation coefficients were 0.953, 0.930, 0.958, 0.857, 0.913 and 0.951, respectively, for each measurement. All six measurements were significantly larger for males (P < 0.001). Multiple regression analysis demonstrated a significant relationship between gender and rim length for all six measurements (P < 0.001) and between height and leg length and acetabular rim length for five of the six measurements exclusive of AIIS-anterior (P < 0.001). No significant trends between age or ethnicity and rim length were found. Average acetabular rim lengths were established. The acetabular rim is significantly longer in males and correlates with height and leg length. Age and ethnicity do not appear to be significant predictors of acetabular rim length. Normative values for acetabular rim lengths may assist in hip preservation surgery.

Avulsion of the direct head of rectus femoris following arthroscopic subspine impingement resection: a case report

Arthroscopic resection of the anterior inferior iliac spine (AIIS) for subspine impingement has become a relatively common procedure. The AIIS is the origin of the direct head of rectus femoris (dhRF). Previous studies have reported that removal of the contributing portion of the AIIS causing impingement is unlikely to weaken the attachment of the dhRF. The purpose of this article is to report a case of avulsion of the dhRF, following revision hip arthroscopy for the treatment of subspine impingement. A 23-year-old professional footballer underwent revision left hip arthroscopy for the treatment of subspine impingement. 5-mm of bone was resected inferior to the AIIS. Two-weeks post-operatively, he presented with sudden onset, severe left anterior thigh pain following a fall and hyperextension of his left hip. The patient felt a pop over the anterior aspect of his hip. He noticed immediate swelling, severe pain and stiffness. Examination revealed diffuse swelling, 4/5-power on straight-leg-raise, focal tenderness over the AIIS but no palpable gap. MRI confirmed the clinical suspicion of a dhRF avulsion. Given the minimal loss of power and the lack of significant retraction, the patient was treated conservatively. He was instructed to avoid excessive hip extension. He returned to full participation at 3-months. This article highlights a case of avulsion of the dhRF due to a hyperextension injury of the hip following arthroscopic resection of subspinal impingement, a previously unreported complication. Resection of soft and bone from the AIIS may weaken the insertion of the dhRF. Care should be taken during post-operative rehabilitation to avoid trauma and excessive forces on the dhRF tendon, which may lead to rupture. Rehabilitation should be focused on range of motion of the hip.

Hip impingement: beyond femoroacetabular

In the last 20 years, femoroacetabular impingement has been at the forefront of clinical practice as a cause of hip pain in young adults. As arthroscopic techniques for the hip continue to evolve, the possible presence of a new group of conditions creating mechanical conflict in and around the hip joint (ischiofemoral, subspine and iliopsoas impingement) has recently been elucidated whilst interest in already known 'impingement' syndromes (pelvic-trochanteric and pectineofoveal impingement) is now revived. This article attempts to increase awareness of these relatively uncommon clinical entities by describing their pathomorphology, contact mechanics, treatment and published results available to present. It is hoped that such knowledge will diversify therapeutic options for the clinician, thereby improving outcomes in a small but not negligible portion of patients with previously unexplained persistent symptoms.

Comparison of polyethylene wear in anatomical and reversed shoulder prostheses

Wear of polyethylene is associated with aseptic loosening of orthopaedic implants and has been observed in hip and knee prostheses and anatomical implants for the shoulder. The reversed shoulder prostheses have not been assessed as yet. We investigated the volumetric polyethylene wear of the reversed and anatomical Aequalis shoulder prostheses using a mathematical musculoskeletal model. Movement and joint stability were achieved by EMG-controlled activation of the muscles. A non-constant wear factor was considered. Simulated activities of daily living were estimated from in vivo recorded data.

After one year of use, the volumetric wear was 8.4 mm3 for the anatomical prosthesis, but 44.6 mm3 for the reversed version. For the anatomical prosthesis the predictions for contact pressure and wear were consistent with biomechanical and clinical data. The abrasive wear of the polyethylene in reversed prostheses should not be underestimated, and further analysis, both experimental and clinical, is required.