Aims. Developmental cervical spinal stenosis (DcSS) is a well-known predisposing factor for degenerative cervical myelopathy (DCM) but there is a lack of consensus on its definition. This study aims to define DcSS based on MRI, and its multilevel characteristics, to assess the prevalence of DcSS in the general population, and to evaluate the presence of DcSS in the prediction of developing DCM. Methods. This cross-sectional study analyzed MRI spine morphological parameters at C3 to C7 (including anteroposterior (AP) diameter of spinal canal, spinal cord, and vertebral body) from DCM patients (n = 95) and individuals recruited from the general population (n = 2,019). Level-specific median AP spinal canal diameter from DCM patients was used to screen for stenotic levels in the population-based cohort. An individual with multilevel (≥ 3 vertebral levels) AP canal diameter smaller than the DCM median values was considered as having DcSS. The most optimal cut-off canal diameter per level for DcSS was determined by receiver operating characteristic analyses, and multivariable logistic regression was performed for the prediction of developing DCM that required surgery. Results. A total of 2,114 individuals aged 64.6 years (SD 11.9) who underwent surgery from March 2009 to December 2016 were studied. The most optimal cut-off canal diameters for DcSS are: C3 < 12.9 mm, C4 < 11.8 mm, C5 < 11.9 mm, C6 < 12.3 mm, and C7 < 13.3 mm. Overall, 13.0% (262 of 2,019) of the population-based cohort had multilevel DcSS. Multilevel DcSS (odds ratio (OR) 6.12 (95% CI 3.97 to 9.42); p < 0.001) and male sex (OR 4.06 (95% CI 2.55 to 6.45); p < 0.001) were predictors of developing DCM. Conclusion. This is the first MRI-based study for defining DcSS with multilevel canal narrowing. Level-specific cut-off canal diameters for DcSS can be used for early identification of individuals at risk of developing DCM. Individuals with DcSS at ≥ three levels and male sex are recommended for close monitoring or early intervention to avoid traumatic spinal cord injuries from stenosis. Cite this article: Bone Joint J 2024;106-B(11):1333–1341

Introduction: Sports injuries to the cervical spine account for about one in ten of all cervical spine injuries. They occur at all levels of participation. Fortunately, the number of patients suffering spinal cord injury is relatively small. Neurological injuries may range from transient quadriparesis through to complete quadriplegia. The decision to allow sportsmen to return to sport following a cervical spine injury is complex. It is based on such factors as history, clinical examination, the nature of the injury, as well as age and other psychosocial factors. The evidence that exists to aid this decision process is at times conflicting. The aim of this presentation is to review some of the contentious issues that exist in the decision making by reference to case presentations of high level sportsmen who were treated following a variety of cervical spine injuries. Methods: Four high-level rugby players (22–31 years old) presented with different cervical spine injuries sustained during sporting activities. Two subjects sustained a “stinger” and two a transient quadriparesis which rapidly resolved. Radiological evaluation included assessment of spinal canal diameter. 1. Results: Two had a C5-6 disc bulge with developmental spinal stenosis. A third had a congenital fusion C2-3 with a disc bulge and developmental stenosis at C3-4. Case 4 had degenerative disc disease at C5-6. All were treated non-operatively and returned to sport. All suffered a recurrence of the neurological symptoms and subsequently underwent an anterior interbody fusion (Case 4 for subluxation of C6-7). Three successfully resumed rugby six months after surgery while one elected not to continue. Discussion: The decision to allow a patient to return to contact sports following a cervical spine injury may be difficult. The four cases presented highlight some of these contentious issues such as transient neurological deficit and the effect that surgery may have on a patient’s ability to return safely to sport. A review of the literature may assist in the decision making. 1,. 2. This may be conflicting and difficult to interpret. Neurological signs, instability, displacement, fusion of more than one level and occipito-atlanto-axial pathologies are considered absolute contraindications. 3

Introduction Cervical cord neuropraxia (CCN) and incomplete cord injuries such as central cord syndrome (CCS) are more prevalent in patients with congenitally narrow spinal canals. At Middlemore Hospital, Polynesian and Maori males are frequent in that group of patients who have experienced a single episode of CCN or CCS. The aim of this study was determine if these racial groups were over-represented in patients with incomplete cord injuries, and if there was an ethnic variation in mid-sagittal diameter of the cervical spine in the general population. Methods A chart review of all patients who experienced either CCS or CCN in the absence of significant fracture dislocation or disc prolapse was performed. The ethnic origin of these patients was noted. CT scan was used to measure the mid-sagittal diameter of the spinal canal from C3 to C7 in a group of 166 sequential trauma patients who had CT scans of the cervical spine at Middlemore Hospital. Patient’s race was that declared by the patient. Four different observers used computer digitisation to measure the mid-sagittal diameters and mean sagittal diameter for each level. Measurements were compared between races. Results Between 2000 and 2004, eight patients (7 males, 1 female) were noted to have a central cord syndrome or cervical neuropraxia in the absence of fracture dislocation, acute disc prolapse or developmental spinal stenosis. Five patients were Polynesian, two Maori and one European. CT scan assessment of the 166 patients noted Maori cervical spine canals to be 1mm smaller than Europeans (P values less than .005 at all levels of the C-spine) whilst Polynesians had on average 2mm smaller mid-sagittal diameter compared to Europeans (all P values less than 0.001). Discussion Patients with congenital reduction in spinal canal diameter have an increased risk of transient neuropraxia (Torg J. J Bone Joint Surg. 1996), neurological injury (Matsura P et al. J Bone Joint Surg. 1989) and more significant myelopathy in the presence of trauma (Eismont FJ et. al. Spine 1984). This study demonstrates that Polynesians were over-represented in the group of patients who experienced central cord syndrome or transient cervical neuropraxia. CT scan assessment demonstrated that both Maoris and Polynesians had significantly narrower canals than their European counterparts. Previous studies have demonstrated that South African blacks have significantly narrow mid-sagittal diameter than Caucasians (Taitz C. Clin Anat. 1996). The implications of this study are that Maori and Polynesians involved in high impact activities such as rugby may be at increased risk of incomplete or complete spinal cord injuries. There is however no reliable screening tool available for congenital spinal canal stenosis