Dynamic Hip Screw - DHS

Original Editor - Rhiannon Clement
Top Contributors - Rhiannon Clement, Lucinda hampton and Kim Jackson

Introduction

Dynamic hip screw x-ray [image from wikimedia]

The dynamic hip screw (DHS), a femoral head-sparing orthopaedic device, is used to treat femoral neck fractures. Alternately referred to as a pin and plate.

Femoral neck fractures that are undisplaced (Garden I and II fractures) can be treated with head-preserving surgery and internal fixation.

In fractures with a high risk of femoral head avascular necrosis (Garden III and VI fractures), femoral head resection and hip hemiarthroplasty is favoured.

History of the DHS

Prior to the use of DHS sliding screws, angled blade plates were used. These fixed plates matched the angle of the femural head. These plates had a number of complications, including failure to purchase, requiring frequent osteotomies. They also did not allow any compression across the fracture site, leading to stress failures and frequent non-union. Therefore, the DHS, with sliding barrel, was created to allow controlled compression across the fracture site. This is important for bone healing.

NICE Guidelines recommends: Use extramedullary implants such as a sliding hip screw in preference to an intramedullary nail in patients with trochanteric fractures above and including the lesser trochanter (AO classification types A1 and A2).

Physiotherapy Interventions

Considerations post surgery:

• Post op instructions and weight bearing status
• Infections / wound healing
• Neurovascular complications
• Pain
• Self-efficacy and motivation
• Fear of falling

Any transfer or mobility aids will be determined by the weight bearing status (usually highlighted in the op note). If the surgeon feels the hip needs protecting post surgery, they may advise partial or non-weight bearing for the patient.

Physiotherapy interventions:

• Transfers (bed, chair, toiletting).
• Mobility (+/- appropriate aid).
• Goal setting
• Advising patient and team on pain management and expectations post-surgery
• Advice on swelling management
• Exercises
• Balance retraining and confidence building
• Gait retraining
• Considering home environment.
• Interactions with family and carer

It is important that the patient is transferred out of bed, within these limitations, as early as possible to avoid complications of bed rest (e.g. chest infections, DVT, muscle atrophy). NICE guidelines advise, unless contraindicated, for patient's to mobilise the day after surgery.

Physiotherapy exercises post hip surgery:

Illustrations by: https://myhealth.alberta.ca/Alberta/Pages/hip-fracture-hip-exercises.aspx

	After surgery		After 6 weeks
Supine	Hip ABD and heel slides (slide sheet can reduce friction)	Inner Range Quads	Bridges (unless NWB)
Sitting	Knee extension	Knee flexion	Sit to stand (one balance optimised)
Standing	Once able to maintain independent standing balance. Hip Abduction Hip Extension	Hamstring Curl and Marching on the Spot	Heel Raises and Mini squats

Evidence

DHS Vs Hemiarthroplasty:

Compared to hemiarthroplasty, the DHS has been found to have a superior hip functional outcome. However, the DHS has a higher chance of blood loss requiring blood transfusion and complications requiring revisions. Both were comparable for duration of surgery, length of stay in hospital and early mobilisation. Therefore, may have benefits for return to function for a selected patient group.

Internal fixation of NOF:

The FAITH study (2014) suggests that most studies into internal fixation of fractured NOF compare against hemiarthroplasty. This means there is a lack of evidence for different methods of internal fixation. RCTs with direct comparison are too small and lack sufficient power. Therefore, the FAITH study looked at the effects on patients after cancellous screws and sliding screws.

The FAITH study (2017) suggests that both are comparable for revision / reoperation rates at 24 months, but the sliding hip screw group had a greater instance of avasular necrosis. However, this was not a significant difference and the DHS was found to be more beneficial for displaced fractures and reduced rates of reoperation. It was also thought to be beneficial for those with poor bone density, such as smokers. The authors noted that this finding of benefits for displaced fractures was inconsistent with other study findings.

Precautions post surgery

• Post surgical complications
• Intra-capsular surgery may require a period of partial or protected weight bearing to ensure no displacement of the humeral head
• Avasular necrosis of the femural head
• Operation site infections
• Foot drop post-op
• Risk of fracture to bone below metal plate
• Haematoma
• Non-union or malunion

Rarely, the hip screw might protrude into the hip joint articular surface. This can present as increased pain on mobilisation and may result in surgical intervention, such as revision to a hemi to total hip replacement.