Metal implants used to fix broken bones in the hip joint in older adults

This review assessed evidence from randomised controlled trials (RCTs) and quasi-RCTs, on the relative benefits and harms of different metal implants used to treat one type of hip fracture in older adults (aged 60 years or over).

Background

A hip fracture is a break at the top of the leg bone. We included people with a break just below the ball and socket joint. These types of broken hip are common in older adults whose bones may be fragile because of a condition called osteoporosis. They often happen after a fall from a standing or sitting position. A common way of mending this break is to fix the broken parts of bone with metal implants. During an operation, the surgeon may insert a smooth pin or screw through the two parts of broken bone. A smooth pin is not threaded like a screw but may have extra features such as a fold-out hook. Alternatively, the surgeon may use a 'fixed angle plate' which sits on the outer edge of the broken bone and is attached to the bone with screws or pins.

Search date

We searched for RCTs (clinical studies where people are randomly put into one of two or more treatment groups), and quasi-RCTs (in which people are put into groups by a method which is not randomised, such as date of birth or hospital record number), published up to 6 July 2020.

Study characteristics

We included 38 studies, involving 8585 adults with 8590 hip fractures. The average age of study participants ranged from 60 to 84 years; 73% were women, which is usual for people who have this type of hip fracture.

Key results

Smooth pins compared with fixed angle plates (four studies, 1313 participants): we are uncertain whether there is a difference between these implants in improving a person's ability to walk independently (with no more than one walking stick), in the number of people who die early (within four months of surgery) or up to 12 months after surgery, and in how many people need additional surgery (e.g. because of deep infection around the implant).

Screws compared with fixed angle plates (11 studies, 2471 participants): we found no evidence of difference between these implants in hip function (ability to use the hip), health-related quality of life (HRQoL), death at 12 months, and additional surgery. We are uncertain whether there is a difference between these implants in independent walking, and early deaths.

Screws compared to smooth pins (seven studies, 1119 participants): we found no evidence of difference between these implants in deaths at 12 months. We are uncertain whether there is a difference between these implants in early deaths and additional surgery.

Screws or pins compared with fixed angle plates (15 studies, 3784 participants): we found no evidence of difference between these implants in deaths at 12 months, or additional surgery. We are uncertain whether there is a difference between implants in independent walking and early death. We found no additional evidence for hip function or HRQoL.

No studies in the review reported activities of daily living or delirium.

Certainty of the evidence

Although there were some large studies, most of the evidence for each outcome came from only a few participants. Many older studies were not well reported. It was not possible to hide from the surgeons what type of fixing was used, which might affect a surgeon's decision on whether someone needed additional surgery. Sometimes, we found differences between the findings of individual studies that we could not explain.

For these reasons, we assessed the evidence for the outcomes as either low- or very low-certainty evidence. This means we had limited confidence or very little confidence in the results.

Conclusions

There may be little or no difference between screws and fixed angle plates in hip function, HRQoL, deaths at 12 months, and additional surgery, and between screws and pins in deaths at 12 months. But we are uncertain of the effects for other outcomes, including those for smooth pins versus fixed angle plates, because the evidence was very low-certainty. More well-designed RCTs on metal implants will be helpful.

Authors' conclusions: 

There is low-certainty evidence that there may be little or no difference between screws and fixed angle plates in functional status, HRQoL, mortality at 12 months, or unplanned return to theatre; and between screws and pins in mortality at 12 months. The limited and very low-certainty evidence for the outcomes for which data were available for the smooth pins versus fixed angle plates comparison, as well as the other outcomes for which data were available for the screws and fixed angle plates, and screws and pins comparisons means we have very little confidence in the estimates of effect for these outcomes. Additional RCTs would increase the certainty of the evidence. We encourage such studies to report outcomes consistent with the core outcome set for hip fracture, including long-term quality of life indicators such as ADL and mobility.

Read the full abstract...
Background: 

Hip fractures are a major healthcare problem, presenting a huge challenge and burden to patients, healthcare systems and society. The increased proportion of older adults in the world population means that the absolute number of hip fractures is rising rapidly across the globe. The majority of hip fractures are treated surgically. This review evaluates evidence for types of internal fixation implants used in joint-preserving surgery for intracapsular hip fractures.

Objectives: 

To determine the relative effects (benefits and harms) of different implants for the internal fixation of intracapsular hip fractures in older adults.

Search strategy: 

We searched CENTRAL, MEDLINE, Embase, Web of Science, Cochrane Database of Systematic Reviews, Epistemonikos, Proquest Dissertations and Theses, and National Technical Information Service in July 2020. We also searched clinical trials databases, conference proceedings, reference lists of retrieved articles and conducted backward-citation searches.

Selection criteria: 

We included randomised controlled trials (RCTs) and quasi-RCTs comparing implants used for internal fixation of fragility intracapsular proximal femoral fractures in older adults. Types of implants were smooth pins (these include pins with fold-out hooks), screws, or fixed angle plates. We excluded studies in which all or most fractures were caused by specific pathologies other than osteoporosis or were the result of a high energy trauma.

Data collection and analysis: 

Two review authors independently assessed studies for inclusion. One review author extracted data and assessed risk of bias which was checked by a second review author. We collected data for seven outcomes: activities of daily living (ADL), delirium, functional status, health-related quality of life (HRQoL), mobility, mortality (reported within four months of surgery as early mortality, and at 12 months since surgery), and unplanned return to theatre for treating a complication resulting directly or indirectly from the primary procedure (such as deep infection or non-union). We assessed the certainty of the evidence for these outcomes using GRADE.

Main results: 

We included 38 studies (32 RCTs, six quasi-RCTs) with 8585 participants with 8590 intracapsular fractures. The mean ages of participants in the studies ranged from 60 to 84 years; 73% were women, and 38% of fractures were undisplaced.

We report here the findings of the four main comparisons, which were between different categories of implants.

We downgraded the certainty of the outcomes for imprecision (when data were available from insufficient numbers of participants or the confidence interval (CI) was wide), study limitations (e.g. high or unclear risks of bias), and inconsistency (when we noted substantial levels of statistical heterogeneity).

Smooth pins versus fixed angle plate (four studies, 1313 participants)

We found very low-certainty evidence of little or no difference between the two implant types in independent mobility with no more than one walking stick (1 study, 112 participants), early mortality (1 study, 383 participants), mortality at 12 months (2 studies, 661 participants), and unplanned return to theatre (3 studies, 736 participants). No studies reported on ADL, delirium, functional status, or HRQoL.

Screws versus fixed angle plates (11 studies, 2471 participants)

We found low-certainty evidence of no clinically important differences between the two implant types in functional status using WOMAC (MD -3.18, 95% CI -6.35 to -0.01; 2 studies, 498 participants; range of scores from 0 to 96, lower values indicate better function), and HRQoL using EQ-5D (MD 0.03, 95% CI 0.00 to 0.06; 2 studies, 521 participants; range -0.654 (worst), 0 (dead), 1 (best)). We also found low-certainty evidence showing little or no difference between the two implant types in mortality at 12 months (RR 1.04, 95% CI 0.83 to 1.31; 7 studies, 1690 participants), and unplanned return to theatre (RR 1.10, 95% CI 0.95 to 1.26; 11 studies, 2321 participants). We found very low-certainty evidence of little or no difference between the two implant types in independent mobility (1 study, 70 participants), and early mortality (3 studies, 467 participants). No studies reported on ADL or delirium.

Screws versus smooth pins (seven studies, 1119 participants)

We found low-certainty evidence of no or little difference between the two implant types in mortality at 12 months (RR 1.07, 95% CI 0.85 to 1.35; 6 studies, 1005 participants; low-certainty evidence). We found very low-certainty evidence of little or no difference between the two implant types in early mortality (3 studies, 584 participants) and unplanned return to theatre (5 studies, 862 participants). No studies reported on ADL, delirium, functional status, HRQoL, or mobility.

Screws or smooth pins versus fixed angle plates (15 studies, 3784 participants)

In this comparison, we combined data from the first two comparison groups. We found low-certainty evidence of no or little difference between the two groups of implants in mortality at 12 months (RR 1.04, 95% CI .083 to 1.31; 7 studies, 1690 participants) and unplanned return to theatre (RR 1.02, 95% CI 0.88 to 1.18; 14 studies, 3057 participants). We found very low-certainty evidence of little or no difference between the two groups of implants in independent mobility (2 studies, 182 participants), and early mortality (4 studies, 850 participants). We found no additional evidence to support the findings for functional status or HRQoL as reported in 'Screws versus fixed angle plates'. No studies reported ADL or delirium.

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