Cam femoroacetabular impingement (FAI) is currently treated by resecting the femoral cam lesion. Some surgeons advocate additional anterosuperior acetabular rim resection. However, the exact acetabular contribution to cam-FAI has yet to be described. Using 3D-CT analysis, we set out to quantify the acetabular rim shape and orientation in this condition, and to determine the roles of these factors in cam-FAI.

The acetabula of twenty consecutive cam hips (defined by α-angle of Notzli greater than 55° on plain radiographs) undergoing image based navigated surgery. These were compared with twenty normal hips (defined as disease free sockets with a normal femoral head-neck junction) obtained from a CT colonoscopy database.

Using 3D reconstruction software, the pelvis was aligned to the anterior pelvic plane (APP). Starting at the most anterior rim point, successive markers were placed along the rim. A best-fit acetabular rim plane (ARP) was derived, and the subtended angle (SA) between each rim marker and a normal vector from the acetabular centre was calculated. Values above 90° indicated a peak, with less than 90° representing a trough. Inclination and version were measured from the APP.

Our results showed that the rim profile of both cam-type and normal acetabular is an asymmetric succession of three peaks and three troughs. However, the cam-type acetabulum is significantly shallower overall than normal (Mean SA: 84±5° versus 87±4°, p< 0.0001). In particular, at anatomical points in the impingement zone between 12 and 3 o’clock, the subtended angle of cam hips were never higher than normal, and, in fact, at certain points were lower (iliac eminence: 90±5° vs. 93±4° p=0.0094, iliopubic trough: 79±5° vs. 83±4° p=0.0169, pubic eminence 83±7° vs. 84±4° p=0.4445). The orientation of cam and normal hips were almost identical (Inclination: 53±4°vs. 51±3° p=0.2609 and Anteversion: 23±7° vs. 24±6° p=0.3917).

We concluded that cam-type acetabula are significantly shallower than normal. The subtended angles at all points around the hip were lower, and in particular, in the impingement zone between 12 and 3 o’clock not one cam had a subtended angle over 90°. We have therefore been unable to support the hypothesis of mixed-type FAI in cam-type hips.

Bony rim resection in cam hips therefore runs the risk of rendering the acetabulum more morphologically abnormal and even functionally dysplastic. We do not recommend acetabular rim resection in patients with pure cam-type impingement, and await the longer-term results of this practice with apprehension.

Pincer femoroacetabular impingement (FAI) is cited as being the result of a socket that is either too deep or retroverted, or both. Using 3D-CT analysis, we set out to quantify the acetabular rim shape and orientation to determine the roles of these two factors in FAI.

Twenty pincer acetabulae were selected from patients undergoing image based navigated surgery, where the lateral centre edge angle was greater than 40° on plain radiographs. The normal group of disease free sockets were obtained from a CT colonography database.

Using 3D reconstruction of their CT scans, a novel method of mapping the acetabular rim profile was created. The pelvis was aligned to the anterior pelvic plane. Starting at the most anterior rim point, successive markers were placed along the rim. A best fit plane (ARP) through the acetabulum was derived, and the subtended angle (SA) between each rim marker and a normal vector from the acetabular centre was calculated. Values above 90° indicated a peak, with less than 90° representing a trough. Inclination and version were measured from a horizontal plane and the ARP, in the coronal and axial view respectively.

The results showed that asymmetric acetabular rim profiles in normal and pincer hips were very similar. However, pincer hips are significantly deeper overall (Mean SA 96±5° vs. 87±4° p< 0.00001) and at each anatomical point of the three eminences (pubic [SA: Normal 84±4° vs. Pincer 94±7° p< 0.00001], iliac [SA: 93±4° vs. 100±6° p=0.00021] and ischial [SA: 92±3° vs. 102±8° p=0.00005]) and two troughs (ilio-pubic [SA: Normal 83±4° vs. Pincer 94±8° p=0.00001] and ilio-ischial [SA: 92±3° vs. 102±8° p=0.00002]).

The orientation of normal and pincer were almost identical (Inclination: 51±3° vs. 51±6° p=0.54 and Version: 24±6° vs. 25°±7° p=0.67).

We conclude that the rim shape of pincer hips follows the same contour as normal hips. In agreement with current radiographic diagnosis, pincer-type hips are characterised by a deeper acetabulum. This ‘overcoverage’ of the femoral head confirms the biomechanical model of pincer-type impingement.

Both inclination and version in these two groups were almost identical, with no truly retroverted acetabulum seen. Pincer impingement resulting from ‘acetabular retroversion’ is a concept currently based upon radiographic signs that we have been unable to confirm in this small 3D study using the subtended angle as the key descriptor of acetabular morphology.

The aetiology and pathophysiology of frozen shoulder is poorly understood. The macroscopic pathological finding is dense fibrosis of the glenohumeral capsule and ligaments. Cellular histological studies reveal active proliferation of fibroblasts and their transformation to myofibroblasts, resulting in a dense matrix of disorganised collagen, causing capsular contracture. To further elucidate these pathological changes we arthroscopically examined 45 consecutive frozen shoulders immediately prior to performing arthroscopic release.

The distinctive finding in all cases was new blood vessel formation or angiogenesis in the synovium and capsule. There were five distinct angiogenic patterns: 1.vascular synovial proliferation at the base of the anchor of the long head of biceps tendon (most common); 2.petechial haemorrhagic spots widely spread across the synovium, in the rotator interval and even on the labral surface; 3.capillary loops and spirals, appearing like “lava flow”; 4.dense red vascular synovitis; 5.spectacular capillary whorls, similar in appearance to glomeruli (least common). High quality arthroscopic digital images will illustrate these findings.

The vascular changes seen in the shoulder joint in frozen shoulder are pathognomonic and similar to those seen in the formation of hypertrophic and keloid scarring of the skin, diabetic retinopathy, a variety of auto-immune disorders and tumours, rheumatoid arthritis and many other disease processes. The ability to therapeutically inhibit angiogenesis via inhibition of cytokines or adhesion molecules in these diseases suggests a possible role for these developing non-surgical treatments in frozen shoulder.

Displaced proximal humeral fractures are notoriously difficult to treat. We performed internal fixation of 55 such fractures with the Polarus locked intramedullary nail. 43 (78%) were women; the mean age was 74 (range 15–91). The mechanism of injury was RTA in four, sporting injury in a further four and a simple fall in 47 (85%). According to Neer’s classification, 25 were two part fractures, 20 three part and 10 four part. 47 fractures were fixed acutely (within seven days).

The average operative time, including patient positioning was 60 minutes. In 43 cases the standard size nail was used (11mm diameter, 150mm length). In the majority of cases (80%) either two or three proximal locking screws were used. In 15 cases (27%) open reduction was necessary.

Patients were followed up for an average of eight months. Three patients needed removal of backed out proximal screws under local anaesthetic. In one patient the nail migrated superiorly and was removed once the fracture had united. One patient developed symptomatic avascular necrosis of the humeral head, successfully treated by removing the proximal screws. Two patients developed fracture malunion and underwent conversion to hemiarthroplasty. One patient required arthroscopic release of a secondary frozen shoulder.

Patients completed an Oxford Shoulder questionnaire at an average of 18 months postoperatively (range 5–42 months). The median Oxford Shoulder score was 33 (95% CI 25–38) with a mean score of 34.6

Previous studies of Polarus nailing have reported satisfactory results, but with limited follow up of a small number of patients. Our study of 55 cases with an average 18 month follow up confirms good functional rapid recovery in the majority of patients. Only five patients required removal of the metalwork and only two patients required conversion to hemiarthroplasty. We recommend the Polarus nail as a useful addition to the shoulder trauma surgeon’s armamentarium.