Anterior cruciate ligament (ACL) injuries are frequent among athletes and a leading cause of time away from competition. Stability of the knee involves the ACL for limiting anterior tibial translation and the ALL (anterolateral ligament) to restrain internal rotation of the tibia. Present indications for treatment with a combined ACL-ALL reconstruction remain unclear and mostly subjective. We mathematically modeled the tibial plateau geometry to try and identify patients at risk of ACL injury, and develop an objective trigger point for the decision to proceed with additional surgery to optimize rotational stability in these higher risk patients. We hypothesized that an increased convexity and steepness of the posterior aspect of the lateral plateau would subject knees to higher rotational torques leading to potentially a higher risk of ACL injury.

The study design was a case-control study involving ACL reconstruction cases (n=68) and matched controls (n=68) between 2008–2015 at our institution. We used a two-dimensional approach, evaluating sagittal MRI images of the knee to model the posterior convexity of the lateral tibial plateau. Points were selected along the articular surface, and a least-squares regression was used to curve-fit a power function (y = a xn). In the equation, larger coefficient a and n represented steeper slopes. The cases and controls were compared using a Mann-Whitney-U test, and the statistical significance was set at α < 0.05. A subgroup analysis for females and males was also performed for the curve-fit coefficients.

We observed a significant difference in the tibial surface geometry between our ACL reconstruction cases and matched controls (Figure 1). The modeled power equation for our ACL cases had larger coefficients compared to controls for all groups. For all pooled subjects, coefficient a (ACL recon cases = 0.90 vs controls = 0.68, p < 0.0001) and coefficient n (ACL recon cases = 0.34 vs controls = 0.30, p = 0.07) (Table 1). For the statistically significant coefficient a, we found it had a sensitivity of 78.9% and specificity of 77.5% for the statistically significant coefficient a, we found it had a sensitivity of 78.9% and specificity of 77.5% for predicting injury, using a cut off coefficient of a = 0.78. The odds ratio was 12.6 [5.5 – 29].

The posterolateral cartilaginous slope of the tibial plateau was mathematically modeled in patients with ACL injury. Patients with ACL injury demonstrated abnormally steep and fast slopes compared to controls that may play predispose to ACL injury by increasing anterior translation forces and internal rotation torques sustained by their knee joint. A steeper slope may also explain high-grade pivot shifts on physical exam that are thought to be a relative indication for adding an associated ALL reconstruction. Our findings are promising for adding more objectivity to surgical decision-making, especially with identifying high-risk patients that may be candidates for combined ACL-ALL reconstructions.

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Introduction

The Medicines and Healthcare Products Regulatory Agency (MHRA) of the UK have published guidelines for annual follow up of patients with metal on metal hip replacements following widespread concern regarding metallosis

The Royal Marines regularly deploy to Norway to conduct Cold Weather, Arctic and Mountain Warfare training. A total of 1200 personnel deployed to Norway in 2010 over a 14-week period. Patients, whose injuries prevented them from continuing training, were returned to the UK via AEROMED. The aim of this investigation was to describe the epidemiology of musculoskeletal injuries during cold weather training.

All data on personnel returned to the UK was prospectively collected and basic epidemiology recorded.

53 patients (incidence 44/1,000 personnel) were returned to the UK via AEROMED. 20/53 (38%) of cases were musculoskeletal injuries (incidence 17/1000 personnel). 15/20 musculoskeletal injuries were sustained while conducting ski training (incidence 13/1,000): 4/20 were non-alcohol related injuries, 1/20 was related to alcohol consumption off duty. Injuries sustained whilst skiing: 5/15 sustained anterior shoulders dislocation, 5/15 Grade 1-3 MCL/LCL tears, 2/15 sustained ACJ injuries, 1/15 crush fracture T11/T12, 1/15 tibial plateau fracture and 1/15 significant ankle sprain. Non-Training injuries: 1 anterior shoulder dislocation, 1 distal radial fracture, 1 olecranon fracture, 1 Scaphoid Fracture and one 5th metatarsal fracture. 60% of injuries were upper limb injuries. The most common injury was anterior shoulder dislocation 6/20 (Incidence 5/1000)

Our results suggest that cold weather warfare training has a high injury rate requiring evacuation: 4% of all people deployed will require AEROMED evacuation, and 2% have musculoskeletal injuries. Ski training causes the majority of injuries, possibly due to the rapid transition from non-skier to skiing with a bergen and weapon. Military Orthopaedic and rehabilitation units supporting the Royal Marines, should expect sudden increases in referrals when large scale cold weather warfare training is being conducted. Further research is required to see if musculoskeletal injury rates can be decreased in cold weather warfare training.